This is a very important point to remember about subterranean tunnel systems. It is exactly what came to my mind when I watched the Boring Company video about a huge network of 3D tunnels. The tech press, which had probably never even covered a construction project yet alone tunnels, was basically like "what about earthquakes"? But tunnel collapse is not the primary safety issue.
It's fires. Smoke and toxic gases from fires spread very quickly through tunnels.
I am a huge fan of the concept, by the way, but I want to emphasize that most fatalities from traffic tunnels have been from fires (apart from ordinary traffic accidents). And Elon Musk has stated that what makes this vision feasible from a cost perspective is smaller tunnel diameters. Which makes air "communication" all the more accelerated and safety critical. Thus any vision of tunneling without detailing fire safety, evacuation systems and firefighter access is significantly incomplete, as these can add significant cost and fundamentally constrain designs.
It's not just the confined-space aspect that causes the fire gases to have such high lethality (although it's certainly extremely significant), it's also the rate of gas production.
Most solids and liquids don't actually burn; they emit flammable gases when exposed to heat, and it's those gases which actually undergo combustion. These gases are created by endothermic processes (pyrolysis and evaporation), and the more heat is available to convert unreactive solid/liquid combustibles into reactive gases, the faster the fire will burn. Therefore, less heat loss (to the outside environment or to non-combustibles) will enable a higher combustion rate and the fire will produce more heat.
Tunnels are quite good at retaining heat, so most of the heat produced by a fire will feed back right into heating combustibles -- enabling devastating heat release rates in the tens to hundreds of megawatts. The heat release rate is roughly proportional to the fire's fuel consumption rate; which will be roughly proportional to the rate of lethal gas (CO/HCN/CO2) production and oxygen depletion.
The radiant heat flux alone can make the fire unapproachable by even appropriately-equipped firefighters -- the massive production of superheated, oxygen depleted, CO/HCN-containing gases can kill -- far beyond the range that the heat flux is deadly.
5-6 atmospheres would be PRESSURIZED, not vacuum.
Also, a vacuum would pull in water from the water table, you'd need pressure to keep it out.
Vacuum would be good for fire prevention, things can't burn if there's no oxygen. Pressure, on the other hand, will greatly amplify fire, if you just pressurize air. If you want to avoid that, you have to pressurize with a neutral gas like nitrogen, which would be expensive if there is any regular amount of gas leakage.
In either case, you'd have to build compartments that were pressure/vacuum proof (think a submarine or spacecraft) -- and in either case, leaving the pressure vessel would pose dire risks to occupants.
I'll try to watch the video when I'm back on WiFi.
> Exactly. And looking at tunneling technology, it turns out that in order to make a tunnel, you have to — In order to seal against the water table, you've got to typically design a tunnel wall to be good to about five or six atmospheres. So to go to vacuum is only one atmosphere, or near-vacuum. So actually, it sort of turns out that automatically, if you build a tunnel that is good enough to resist the water table, it is automatically capable of holding vacuum.
The miners are below the surface and not at 1 atm, so any gauge measures taken there would be psid.
"Some victims escaped to the fire cubicles. The original fire doors on the cubicles were rated to survive for two hours. Some had been upgraded in the 34 years since the tunnel was built to survive for four hours. The fire burned for 53 hours and reached temperatures of 1,000 °C (1,830 °F), mainly because of the margarine load in the trailer, equivalent to a 23,000-litre (5,100 imp gal; 6,100 US gal) oil tanker, which spread to other cargo vehicles nearby that also carried combustible loads."
It was days before the tunnel cooled enough for recovery crews to enter.
Cars are transported on skates, so the engines aren't running during the fire, reducing noxious fumes in the tunnel.
Cars are controlled automatically, reducing the chance of collision.
Since the skates for he cars are controlled automatically, they can be stopped/rerouted much earlier, avoiding bunching cars near the fire.
Michael Punke, the author of the Revenant, wrote an excellent non-fiction book about it called "Fire and Brimstone: The North Butte Mining Disaster of 1917".
If you search for "stench gas" you will find some... interesting photos of the control panel for these systems:
(Something about buttons marked "release stench gas" and "release anti-stench gas" seem amusing in a rather comical fashion.)
We scan information faster in the preferred reading direction, and flipping the warning gas on half a second earlier will likely, sooner or later save somebody from harm. Not that there aren't other ways to improve safety in mines, but each small part counts, I guess?
Unlike carbon monoxide this compound had a very "this will kill you" smell to it.
It smells like sulfur + burnt rice crackers to me... It's actually not that dangerous of a compound - I've spilled it on myself gloveless and it's not a big deal.
Also a bit of a possibly overpedantic note - you can run gels without reducing the disulfide bonds, but typically those proteins will run through the gel faster, not slower because of a more compact form. Because not all proteins have disulfides, if you reduce them first, it creates a predictable relationship between the protein size and the migration velocity, which is the desirable property, not speed.
I guess it's used where clear or somewhat- clear plastic is used. But does BPA have the same smell over time?
my shitty screwdrivers have the smell you're talking about.
Dude even still writes root logs:
Whenever a big event happens, like some big e2 celebrity dies, there's a surge of people logging into the site to pay their respects. Weddings and funerals, they say, but for e2 it seems to be only funerals.
Right now the smells are simple signals; I'm curious if a scent could be engineered to contain a language. Like paper and writing.
I'm asking for my story, in which sapient rats struggle against two-legged monsters with opposable thumbs.
Had it go off on a couple sites I've been on, and it's remarkable how it reaches every corner of the mine.
And if you want to buy some: http://www.zacon.ca/stench-gas.asp
They use wasabi.
Found it... https://youtu.be/kH5JhYsfNMA?t=1m10s
Nowadays my sister suffers claustrophobia & I feel most comfortable shoved into small crooks. But I think I was mostly offset by anxiety related to ventilation
Visited Timmins this May, another northern Ontario city. It was snowing